The present invention relates generally to a system for positioning dies in a machine or press, and more specifically, to a system for transferring dies from a pre-staging table to a machine or press thereby allowing a die to be easily and accurately adjusted in at least two directions so that an operator can quickly and precisely locate the die in the machine or press without external assistance.
Machines, especially presses, typically utilize a plurality of different dies to produce a plurality of different parts. If production schedules require that a single machine or press produce more than one part number, then the dies must be changed each time the schedule calls for the production of another part number. In the past, it was conventional for a fork lift operator to deliver the new die from a remote storage location for each job change and then to assist the machine operator with the positioning of the die in the machine. It is obvious that die changes completed in this manner are wasteful and uneconomical in that they interrupt machine operation and are time consuming by requiring exact positioning of the die in the machine and thus, reduce machine utilization.
In the past, machine utilization was maximized by scheduling lengthy part runs which kept the number of die changes to a minimum. However, this system resulted in inflexible production schedules and could not be readily changed without adversely affecting machine utilization and the dependent assembly operations.
If an assembly operation utilizing the just-in-time concept was supplied by a machine or press, an increased number of die changes was required in order to meet the production schedules and thus, would most likely unacceptably reduce machine utilization.
Previous attempts to minimize die changeover time include the use of tables located adjacent the machine to support a die prior to being positioned in the machine. One example of such a die staging table is disclosed in U.S. patent application Ser. No. 914,692, the disclosure of which is hereby incorporated by reference, filed 2 Oct. 1986, which is commonly owned by the assignee of the present invention. This die staging table includes a top surface consisting of ball transfers on uniform centers. The ball transfers are attached to form steel strips which in turn are attached to a welded steel frame work. A plurality of dies can be pre-positioned on the die table both before and after utilization in the machine or press.
While the die staging table mentioned above reduced a certain amount of die changeover time, by allowing the die to be positioned adjacent the press and to be rolled up to the machine bolster by the operator without help, dies weighing in excess of 1500 pounds still required that the machine operator receive some sort of assistance when positioning the die in the machine or press.
Die transfer systems are presently available for properly positioning a die on a bolster in the press. An example of such a die transfer system is disclosed in U.S. Pat. No. 4,498,384 issued 12 Feb. 1985, the disclosure of which is hereby incorporated by reference. This transfer system includes a pair of elongated, parallel upwardly opening cavities having horizontally extending vertical moveable rails therein. A plurality of rollers are supported by each rail so as to be moveable vertically therewith. An air bag extends longitudinally of each of said cavities under the rails and is engageable with the bottom thereof. Air bag inflation effectuates elevation of the rails and rollers into engagement with the bottom of a die and thereby elevates the die relative to the press bolster.
While this particular system greatly reduced the amount of effort required to transfer the die into the bolster, this particular system was effective to make the transfer in only one direction.
Multi-directional systems are also currently available, examples include hydraulic die lifters and spring loaded die lifters available from Raster Machinery Inc. These systems have precision ball bearings which allow for a full 360.degree. movement of the die on the bolster.
While these spring loaded and hydraulic die lifters allowed for precise location of the die within the press, the complex hydraulic systems associated with these hydraulic die lifters caused significant maintenance problems and were not always available to assist the operator in positioning the die on the bolster and dirt in roller housing added to effort in positioning. The spring loaded lifters were not retractable and were not of sufficient strength to lift heavy dies for proper positioning. Additionally, the springs fatigued and needed to be replaced regularly.
Thus, there is a need for a die handling and location system which provides for at least two directional positioning of the die on the machine bolster; which allows an operator to accurately and rapidly position a die in excess of 1500 lbs. on the press without outside assistance; which provides maximum machine utilization; which provides high reliability and which provides for low maintenance cost.